Fluid Power - Tech

With a traditional manual transmission, engine output is routed through a clutch mechanism to a geardrive assembly. However, in front of every automatic transmission sits a torque converter used to provide the transfer of power from the engine to the internal gearsets in the automatic transmission. The torque converter transfers this power through pressurized fluid flow.

The torque converter housing is bolted to a flexplate or flywheel attached to the rear of the engine crankshaft. Via fluid coupling, power is transmitted from inside the torque converter to a splined input shaft on the automatic transmission. The converter also serves as a torque multiplier (by a factor of 2 or more) as you accelerate from a standstill and allows the engine to idle in gear without moving. It also allows for smooth gearshifts and drivetrain slippage momentarily while gear changes are made without affecting vehicle speed.

There are three major components within a torque converter: impeller, stator, and turbine. The housing bolts to the engine flexplate and provides an enclosed area for these parts to perform their fluid coupling function. The impeller, sometimes called the pump, is attached to one half of the housing. The turbine mates directly to the splined transmission input shaft. Inside each of these two pieces that face each other is a series of metal fins where the transmission fluid circulates. As the impeller spins, it directs fluid to the turbine, which also begins to spin and push fluid back toward the impeller.

In between the impeller and turbine lies the stator. The stator has the job of redirecting the fluid coming from the turbine such that it flows into the impeller in the same direction that the engine is rotating. This reverse operation helps assist the engine rotation. Within the stator is a one-way clutch that allows this action to complement engine rotation but freewheel as vehicle speed increases.